This invention relates to RF voltage/current sensor apparatus and more particularly to broad-band RF voltage/current sensor apparatus or directional couplers.
An RF voltage/current sensor apparatus is a device which samples a small portion of the energy of a wave signal which is traveling through a transmission line. The sensor apparatus may be thought as comprised of a first circuit to sample the voltage on the transmission line and a second circuit to sample the current on the transmission line. These samples provide two voltages which are then used to add for current in one direction and subtract for current in the opposite direction.
Prior art voltage/current sensor apparatus or directional coupler designs were often comprised of a either a capacitive-resistance voltage divider and a loop current probe or capacitive voltage dividers with inserted resistance in the main transmission line. Modifications of these designs eliminated the resistance inserted directly into the transmission line while replacing it with resistance coupled to the transmission line through mutual inductance. While these types of sensors have proven satisfactory they generally are limited to a fairly narrow frequency range.
There exists a need for an improved RF voltage/current sensor apparatus that is less bandwidth limited by its components operational parameters than those known in the prior art.